[PATCH v2 0/2] powerpc/papr_scm: add support for reporting NVDIMM 'life_used_percentage' metric

[Vaibhav Jain <vaibhav@linux.ibm.com>]

Changes since v1 [1]:

* Minor restructuring of code as suggested by Ira
* Renaming of few members of 'struct par_scm_perf_[stat|stats]'
* Fixed a bug where a NULL pointer was potentially passed to
virt_to_phys().
* Using Big endian type rather than cpu native type so receive data
from PHYP in 'struct par_scm_perf_[stat|stats]'
* Some minor log message improvements.

[1] https://lore.kernel.org/linux-nvdimm/20200622042451.22448-1-vaibhav@linux.ibm.com
---

This small patchset implements kernel side support for reporting
'life_used_percentage' metric in NDCTL with dimm health output for
papr-scm NVDIMMs. With corresponding NDCTL side changes [2] output for
should be like:

$ sudo ndctl list -DH
[
  {
    "dev":"nmem0",
    "health":{
      "health_state":"ok",
      "life_used_percentage":0,
      "shutdown_state":"clean"
    }
  }
]

PHYP supports H_SCM_PERFORMANCE_STATS hcall through which an LPAR can
fetch various performance stats including 'fuel_gauge' percentage for
an NVDIMM. 'fuel_gauge' metric indicates the usable life remaining of
an NVDIMM expressed as percentage and  'life_used_percentage' can be
calculated as 'life_used_percentage = 100 - fuel_gauge'.

Structure of the patchset
=========================
First patch implements necessary scaffolding needed to issue the
H_SCM_PERFORMANCE_STATS hcall and fetch performance stats
catalogue. The patch also implements support for 'perf_stats' sysfs
attribute to report the full catalogue of supported performance stats
by PHYP.

Second and final patch implements support for sending this value to
libndctl by extending the PAPR_PDSM_HEALTH pdsm payload to add a new
field named 'dimm_fuel_gauge' to it.

References
==========
[2]
https://github.com/vaibhav92/ndctl/tree/papr_scm_health_v13_run_guage

Vaibhav Jain (2):
  powerpc/papr_scm: Fetch nvdimm performance stats from PHYP
  powerpc/papr_scm: Add support for fetching nvdimm 'fuel-gauge' metric

 Documentation/ABI/testing/sysfs-bus-papr-pmem |  27 +++
 arch/powerpc/include/uapi/asm/papr_pdsm.h     |   9 +
 arch/powerpc/platforms/pseries/papr_scm.c     | 183 ++++++++++++++++++
 3 files changed, 219 insertions(+)

-- 
2.26.2
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